Hydraulic tappet



May 21, 1957 R. c. MOSER HYDRAULIC TAPPET Filed May 31, 1955 w MJ {x11 /nven/or Robe/f C. Maser United States Patent 1 O HYDRAULIC TAPPET Robert C. Moser, Dunedin, Fla.

Application May 31, 1955, Serial No. 512,119

4 Claims. (Cl. 123-90) The present invention relates to an exceptionally simple, economical, easily assembled and operatively eflective hydraulic tappet. I have heretofore obtained Patent No. 2,645,215, with respect to which the present invention is an improvement, being more easily and economically manufactured and assembled and containing novel structure which makes the tappet one of greater surety and dependability in operation. The invention is particularly economical, having few parts, two only of which need to be machine fabricated, the remainder being stock articles purchasable in large quantities at low cost.

My invention is shown in a preferred embodiment in the accompanying drawings, in which,

Fig. 1 is a central longitudinal section through the tappet made in accordance with my invention, the plane of the section being indicated on line 1-1 of Fig. 3, with the tappet as it is when normally operative.

Fig. 2 is a like section with the parts lowered within the tappet body to a lowermost position, in which any dirt, which may be caught against a ball valve located between an upper oil supply chamber of the tappet and a lower pressure chamber thereof, is crushed so that the valve is made automatically properly operative by crushing such dirt, and

Fig. 3 is a horizontal section, looking downwardly, substantially on the plane of line 33 of Fig. 1.

Like reference characters refer to like parts in the different figures of the drawing.

The tappet in its construction includes a cylindrical generally hollow tappet body 1, open at its upper end and having a closed lower end 2, the lower side of which is adapted to bear against a cam on an engine camshaft in the lifting and lowering of the tappet. The outer surface of the body 1 is of uniform diameter except between its upper and lower ends it is provided with a shallow relatively wide groove 3 as shown. The lower end portion may also be reduced in outside diameter though such reduction is not essential. From the groove 3 a radial passage as at 4, one or more of them, extends through the body wall 1 to the interior of the body. Within the body above the groove 3 is an interior continuous annular groove 5 and within the body at its lower end portion the bore of the body is increased in diameter as shown at 6.

A tappet piston of cylindrical form is located within the body being movable lengthwise thereof, the exterior diameter of the piston being slightly less than the interior diameter of the body walls 1. The piston has an upper end portion 7 provided with a recess or socket open at its upper end into which the lower end of an engine valve stem or push rod is adapted to be received. The lower end portion of the piston comprises a cylindrical skirt 8 having an interior cylindrical bore of substantially uniform diameter open at its lower end, and extending upwardly toward but short of the bottom of the socket in the upper end portion 7. A transverse partition 9 separates the socket and skirt portions of the piston as shown.

. Around the piston substantially at such transverse partition 9 a shallow annular groove 10 is cut and from it one or more liquid carrying passages 11 extend into the interior of the body at the upper end of the skirt portion Z ,7 92 ,8 19 Patented May 21, 1957 the lower end of which is of a generally semi-circular cross section. The rib is narrower in width than the thickness of the walls of the skirt portion 8 providing a horizontal exterior annular shoulder at 13 extending outwardly from and around the upper portion of the rib 12. A coiled compression spring 14 has its upper coil surrounding the rib 12 and bears against the shoulder 13, at its lower end being seated against the upper side of the closed end 2 of the tappet body.

A spherical ball valve 15 is below the piston of the tappet. It has a diameter greater than the interior diameter of the piston skirt 8. The lower rounded edges of the rib 12 press against the upper portion of the valve 15 having substantially a circular line contact therewith. Between the under portions of the valve 15 and the upper side of the lower closed end 2 of the tappet body a spring 19 of lesser strength than the spring 14 is positioned. Such spring is of a generally frusto-conical form, the upper coil into which the lower side of the ball valve 15 is received being of smallest diameter and the coils downwardly therefrom progressively increasing in diameter to the lowermost coil which seats against the lower closed end 2 of the tappet body. Such coils when the spring is compressed will nest within each other as shown in Fig. 2, thus the under side of the ball valve 15 in lowermost position will come to and bear against the upper side of such lower end 2.

The ball valve is at the lower end of an oil receiving chamber lfi within the piston skirt 8 above oil in chamber 16 which is under atmospheric pressure. A pressure chamber 17 is below the piston and around the valve 15, the springs 14 and 18 being in such pressure chamber. Preferably the lower end of the valve spring 18 is within a shallow circular recess 19 in the upper side of closed end 2 of the tappet body.

In assembly, spring 18 is first inserted either with or followed by the ball valve 15. The lower end of spring 18, received in the shallow circular recess 19, is centrally located. The heavier spring 14 is then dropped into place after which the piston is inserted. For the purpose, primarily, of holding the parts against separation after assembly and before installing in an internal combustion engine, a circular parted spring snap ring 20 is seated in an interior groove at the upper end of the walls of the tappet body.

In the construction described the strength of the springs 14 and 18 must be carefully considered. The strength of the spring 14 must be greater than the atmospheric pressure over a circular area having the exterior diameter of the tappet piston. The spring 18 must have a strength which, after taking into consideration the weight of the ball 15, is to be less than the atmospheric pressure over an area having the diameter of the chamber 16. Because of the weight of the ball valve 15, the strength of the spring must be less than such atmospheric pressure over a circular area of the interior diameter of chamber 16, plus the ball valve weight. Practically, the weight of the valve 15 may be substantially ignored as negligible under the circumstances.

, in normal operation the parts of the tappet will occupy substantially the position shown in Fig. 1. On the upstroke of a tappet which will lift a valve or a push rod against the force of an engine valve spring which at (3 present, may equal 100 or 110 pounds pressure, the engine oil in the chamber 17 being incompressible, valve 15 will tightly close the end of supply chamber 16. Such pressure will cause a very small quantity of oil to flow or seep upwardly from the pressure chamber 17 between the piston skirt 8 and the walls 1 of the tappet body until it reaches the groove at 10.

On the downstroke of the tappet, when an engine valve which has been lifted reaches its seat, for oil which has escaped from the pressure chamber to be replenished requires that the ball valve 15 shall separate from the rib 12 of the tappet piston. Spring 14 exerting an upward force greater than air pressure downwardly against the upward end of the piston will cause the piston to stay in contact with the valve stem or valve push rod while the spring 18 having less strength than the air pressure over a circular area, the diameter of the chamber 16 will be pushed downwardly by such air pressure, the ball valve 15 separating from the piston whereupon oil will flow from the supply chamber 16 into the pressure chamber 17 until the valve 15 comes against rib 12.

Because the lubricating oil from an internal combustion engine may be contaminated, carrying dirt or other sediment, such dirt or the like may lodge between the rib 1 2 and the surface of the ball valve 15. This will make a gap for oil to flow through between the ball valve and the rib 12. If the dirt is not removed operation of the tappet will be seriously damaged. With the present invention, under such circumstances, upon stopping an internal combustion engine various of the engine valves thereof will be lifted from their seats; and because of the flow gap provided by such lodged dirt the strength of the valve spring exerted against the piston will cause all oil to flow from the pressure chamber 17 into. the supply chamber 16 between the valve 15 and rib 12 so that in a relatively short time, the spherical valve 15 will come against the upper side 2 of the tappet body as in Fig. 2. A solid abutment for the valve 15 is thus made and the heavy pressure of a valve spring will crush dirt between rib 12 and the ball 15. Upon restarting the engine, with spring 14 lifting the piston, oil will flow from the supply chamber 16 to the pressure chamber 17 with rapidity, washing any crushed dirt away and replacing the parts in the normal operative position substantially as in Fig. 1.

The lower end of the tappet body may have the curved form, or substantially segmental spherical surface of relatively large diameter shown, but any other conventional lower end for the valve body may be used for a cam on a camshaft to engage therewith. The inlet passage for the supply of oil to the supply chamber 16 is at the upper conical end of such chamber 16. Air collecting in the upper end of the chamber isreadily removed therefrom and the oil supplied to the chamber 16, though it may carry air bubbles with it uponentry, does. not reach the lower end of such chamber and does not pass into the pressure chamber 17.

It is apparent that the ball valve, the springs 14 and 18 and wire snap ring 21! are stock articles which are purchasable in large quantities at low cost. Only the piston and the tappet body require machining operations. The structure is quickly assembled, is certain in its operations and any momentary defects in operation are automatically cured. The separation of the valve 15 from the rib 12 provides a long passage for oil so that the minute amounts normally required to pass from the supply chamber 16 to the pressure chamber flow almost instantly and at any and all. speeds of engine operation.

The invention is defined in the appended claims and is to be considered comprehensive of all forms of structure coming within their scope I claim:

1. A hydraulic tappet comprising, a hollow tappet body having an open upper end and a closed lower end, a piston within said body longitudinally movable therein .4 having a hollow skirt at its lower end portion of generally uniform outer and inner diameters, open at its lower end, surrounding a liquid supply chamber, a spherical ball valve of greater diameter than the inner diameter of said skirt for closing the lower end of said skirt adapted to engage against the closed end of the tappet body in one position, a lifting spring under said valve between the valve and closed end of the tappet body, and a second stronger lifting spring between the lower end of said skirt and closed end of said tappet body.

2. A hydraulic tappet comprising, a hollow tappet body having an open upper end and a closed lower end, a piston within the body longitudinally movable therein having a skirt at its lower end portion with an upwardly extending bore of generally uniform diameter upwardly from the lower end of said skirt portion, said skirt at its lower open end having a cross sectional annular arcuate surface, a spherical ball valve of greater diameter than said bore against said lower end surface of said skirt, a coiled, enerally conical spring between said valve and closedend of the tappet body having spaced coils collapsible for the lower side of said valve to engage the closed end of said tappet body in the lowermost position of the valve, and a coiled. compression spring of greater strength than the air pressure on an area equal to that of the cross section of said piston disposed between the closed end of said tappet body and the lower end of said piston skirt.

3.. In a hydraulic. tappet having a body with cylindrical walls, an open upper end and a closed lower end, and having a liquid passage through said wall, the improvement comprising, a piston member vertically movable within said body, having a cylindrical skirt lower portion with a closed upper end and a lower open end and a vertical boring within said skirt of generally uniform interior diameter, said skirt at its lower end having an annular rib with a rounded lower edge, and at the upper end of said boring a liquid passage leading from the outer side of the piston member to the interior thereof, a valve body having an upper surface adapted to bear against said rib, and in lowermost position seat against said closed lower end of said body, a lifting spring between the piston member and the lower end of said tappet body, and, a second lifting spring between the valve and said lower end of the tappet body, said second spring havinga Strength less than normal atmospheric pressure upon the upper side of said valve over an area equal to the cross; sectional area of said boring in said piston member.

4. A hydraulic tappet comprising, a hollow tappet body having an. Open upper end and a closed lower end, a piston within said body longitudinally movable therein, having a skirt with walls of generally uniform thickness at its lower; end portion with an upwardly extending bore of uniform diameter upwardly from the lower end of the piston, said skirt at its lower end having an annular downwardly extending ribtherearound of the same inner diameter as said. bore, the lower inner surface of which is of convex arcuate form, a valve having an upper convex, spherical surface portion normally in line contact with the arcuate surface of said rib adapted to close said bore, a spring having a strength less than atmospheric pressure on a circular area equal to that of the circular line contact of said valve and rib normally lifting the valve into contact with said rib, and a heavier spring having a strength greater than atmospheric pressure over a circular area equalling the transverse circular cross sectional area of said piston normally lifting the piston.

References Cited in the file of this patent 

